1. Technical Field
Embodiments of the subject matter disclosed herein generally relate to mechanisms for supporting a liner in a gas turbine, and more particularly, to liner aft end support mechanisms and spring loaded stop liner support mechanisms.
2. Discussion of the Background
In a conventional gas turbine 100 as illustrated in FIG. 1, gases flow from a compressor 110 to a turbine 120 in a gas flow direction 125. The compressor 110 outputs compressed air 127 which is then mixed with fuel 129 input through gas nozzles (not shown). The mixture of air and fuel is burned yielding exhaust gases in a combustion process. The combustion process may occur inside a liner 130. Sometimes, the combustion process occurs inside a combustion chamber (i.e., a component between the compressor and the turbine dedicated to the combustion process) and a liner is used to confine the hot exhaust gases output from the combustion chamber on their path towards the turbine.
The compressed air and fuel are input and mixed at a stop end 135 of the liner 130. The exhaust gases are output through an aft end 140 of the liner 130. The aft end 140 is downstream in the gas flow direction 125 from the stop end 135. The exhaust gases resulting from the combustion are hot causing a thermal expansion of the liner 130. In order to accommodate this expansion, a flexible component, such as, a hula seal 150 is mounted downstream from the liner 130, in the gas flow direction 125. The hula seal 150 allows the aft end 140 of the liner 130 to move along the gas flow direction 125 when a length of the liner 130 is altered due to the thermal expansion.
When the combustion occurs inside the liner 130, the stop end 135 of the liner 130 has a relatively fixed position. Therefore, a liner stop support mechanism 160 is frequently mounted close to the stop end 135, between the liner 130 and a support structure such as a casing (not shown). In contrast, the aft end 140 tends to move along the gas flow direction when the thermal expansion occurs. Therefore, conventionally, no support mechanism is mounted at the aft end 140 of the liner 130.
FIG. 2 schematically illustrates a portion of a gas turbine 200. Gasses flow in a flow direction 205 inside a liner 210 of the gas turbine 200. Compressed air 212 and fuel 213 are mixed inside the liner 210 at a stop end 214. The mixture of compressed air and fuel is burned in a combustion core area 215 of the liner 210. The exhaust gases 216 result from burning the mixture of air and fuel flow from the combustion core area 215 and are output at an aft end 217 of the liner 210. A hula seal (not shown) usually confines the exhaust gases exiting the liner 210 through the aft end 217.
Inside the gas turbine 200, the compressed air 212 enters a space between the liner 210 and a casing 220 surrounding the liner at the aft end and flows towards the stop end where the compressed air is guided inside the liner 210. This manner of guiding the compressed air has the advantage that the compressed air may cool the liner 210. The manner of guiding the compressed air 212 to the stop end 214 of the liner 210 is a design choice. In other embodiments, such as in FIG. 1, the compressed air may be fed inside the liner in other manners.
From an operating temperature point of view, the liner 210 has a liner cold zone 222 located upstream in the flow direction 205 from the combustion core area 215, and a liner hot zone 224 located downstream in the flow direction 205 from the combustion core area 215. Inside the liner 210, the highest gas temperatures are attained in the combustion core area 215. In a first region 226 surrounding the combustion core 215, the gas has temperatures lower than the temperatures in the combustion area. In a second region 227 surrounding the first region 226, the gas has temperatures lower than in the first region 226. In a third outer region 228 surrounding the second region 227, the gas has temperatures lower than temperatures of the second region 227. A person of ordinary skill in the art would understand that the regions 226, 227 and 228 merely illustrate varying gas temperatures inside the liner 210, but no physical separation exists between these regions, the temperature varying continuously inside these regions and across region borders. Also, those skilled in the art would understand that more or less temperature regions may exist.
Heat and vibration from the combustion process, as well as other mechanical loads and stresses from the gas turbine shake, rattle and otherwise cause vibrations of the liner and the other components of the gas turbine in the proximity of the liner. Accordingly, the liner should be mounted such as to withstand the heat, vibration and loads imposed by the combustion and other forces.
A liner stop support mechanism 230 may be mounted between the liner 210 and the casing 220, close to the stop end 214, in the cold zone 222 of the liner 210. Due to its location in the cold zone 222 (where no significant thermal expansion occurs), the liner stop support mechanism 230 connects points relatively fixed on an inner surface of the casing 220, and on an outer surface of the liner 210.
A typical liner stop support mechanism is illustrated in FIG. 3A. The liner stop support mechanism of FIG. 3A includes three individual support elements 350, 352, and 354 disposed between the liner 310 and the casing 320, around a section substantially perpendicular on the flow direction 305.
Each individual support element, e.g., 352 in FIG. 3B, is inserted between pairs of points, one point being located on an inner surface 360 of the casing 320, and the other one being located on an outer surface 370 of the liner 310.
One individual support may have a male part 380 as illustrated in FIG. 3C and a female part 390 as illustrated in FIG. 3D. The male part 380 and the female part 390 are assembled in the manner illustrated in FIG. 3E. A problem with this type of individual support elements is that often contact occurs only between one face of the male part 380 and the female part 390, and this phenomenon leads to uneven wear of the individual support elements.
As mentioned above, due to the hot exhaust gases a thermal expansion of the liner (e.g., 130, 210 or 310) occurs. The thermal expansion of the liner has the effect that the aft end is not held in a fixed position, which prevents the use of a conventional support mechanism at the aft end of the liner (downstream on the flow direction) to which a hula seal is attached. In absence of such a support mechanism, the hula seal supports a substantial load and has more freedom to move than necessary, which leads to a short life cycle of the hula seal and instability in operation.
Accordingly, it would be desirable to provide additional support to a liner and to alleviate the uneven wear of individual support elements in a liner stop support mechanism, thereby avoiding the afore-described problems and drawbacks.